Effects of Electrical Transcutaneous Vagus Nerve Stimulation on the Perceived Intensity of Repetitive Painful Heat Stimuli: A Blinded Placebo- and Sham-Controlled Randomized Crossover Investigation.
This article by a similar group makes a somewhat startling conclusion, but one which I had noticed in the clinic and thought it was spurious. Only in male participants, TVNS was superior to sham and placebo conditions in the reduction